Field of the Invention
The invention relates to a drive for a distributor roller in a printing machine.
German Patent 22 82 16 describes such a drive having a cam disk which is not connected to a motor.
German Patent 24 29 92 describes another such drive having a grooved disk which is rotatable about two axes of rotation, one of which is prescribed or predefined by a pin and is provided for oblique positioning of the grooved disk. The other axis of rotation is prescribed or predefined by bearings of a shaft to which the grooved disk is fixed by the pin, and is not arranged eccentrically to an axis of rotation of the distributor roller.
U.S. Pat. No. 5,540,145 describes yet a further such drive, which is shown in FIG. 2 of the U.S. patent, and has a drive cam to which no adjusting device is assigned for adjusting an inclined position of a cam track of the drive cam.
Because of the constructional conditions of the drives described in the aforementioned patents, the drives are subject to functional restrictions or limitations, or the development of the drives for broadening the functions thereof is not possible.
For example, the amplitude of the axial oscillation of the distributor roller described in the U.S. patent is not variably adjustable.
For this reason, the invention is based upon the concept of providing a drive for the distributor roller, which has constructional conditions permitting function-broadening developments of the drive.
It is accordingly an object of the invention to provide a drive for a distributor roller in a printing machine, which offers the foregoing advantages over heretofore known drives of this general type.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a drive for a distributor roller in a printing machine, comprising a drive cam for driving the distributor roller, the drive cam being formed with a cam track and having a rotational axis axially offset eccentrically with respect to a rotational axis of the distributor roller, the drive cam being drivably connected to a motor for rotating the drive cam about the rotational axis of the cam, and an adjusting device assigned to the drive cam for adjusting an oblique position of the cam track with respect to the rotational axis of the cam.
In accordance with another feature of the invention, the drive cam is disposed on a gear element.
In accordance with a further feature of the invention, the adjusting device includes a planar face formed on the gear element and extending obliquely to the rotational axis of the cam.
In accordance with an added feature of the invention, the adjusting device includes a further rotational axis of the cam obliquely inclined to the first-mentioned rotational axis of the cam.
In accordance with an additional feature of the invention, a fixing device is assigned to the drive cam for securing rotational positions of the drive cam, which are adjusted with respect to the gear element.
In accordance with yet another feature of the invention, the fixing device is a clamping device.
In accordance with yet a further feature of the invention, the motor is drivingly connected to the drive cam via an engageable and disengageable coupling device.
In accordance with yet an added feature of the invention, the motor is drivingly connected to the distributor roller for rotating the distributor roller.
In accordance with yet an additional feature of the invention, the drive includes a further motor drivingly connected to the distributor roller for rotating the distributor roller.
In accordance with a concomitant aspect of the invention, there is provided a printing machine having a drive comprising a drive cam for driving the distributor roller, the drive cam being formed with a cam track and having a rotational axis axially offset eccentrically with respect to a rotational axis of the distributor roller, the dive cam being drivably connected to a motor for rotating the drive cam about the rotational axis of the cam, and an adjusting device assigned to the drive cam for adjusting an oblique position of the cam track with respect to the rotational axis of the cam.
The drive according to the invention for driving a distributor roller in a printing machine is distinguished by the fact that an axis of rotation of a drive cam for driving the distributor roller axially is offset eccentrically in relation to an axis of rotation of the distributor roller, by providing the drive cam with drive connections to a motor for rotating the drive cam about the cam axis of rotation, and by assigning to the drive cam an adjusting device for adjusting an oblique position of a cam track of the drive cam with respect to the cam axis of rotation.
One advantage of this drive is that the amplitude of the axial oscillation of the distributor roller can be adjusted or set variably, by adjusting the oblique position of the cam track.
A further advantage of th e drive according to the invention is that the constructional conditions thereof permit various developments, by which additional functions of the drive, going beyond variation of the amplitude, are made possible.
For example, in the drive according to the invention, it is possible for the motor which rotates the drive cam to be linked, via an electronic control device, to a printing unit of the printing machine so that the motor is rendered inactive by the control device at the beginning of an interruption to the printing unit, and is activated again at the end of the printing interruption. During the printing interruption, therefore, the drive cam is not rotated by the motor and, as a result, the axial back-and-forth or reciprocal movement of the distributor roller, which continues to rotate even during the printing interruption, is brought to a standstill. This is advantageous if the distributor roller is a constituent part of an inking unit which inks a printing-plate cylinder belonging to the printing unit and which has an inking-zone adjusting device for adjusting a zonal inking profile. As a result of stopping the axial distributing movement of the distributor roller, the inking profile in the inking unit is prevented from being leveled completely by the distributor roller during the printing interruption. The action of driving the motor by the control device as described, and based upon switching printing-on and switching printing-off in the printing unit, is advantageous if the motor is a separate motor which is included in the printing machine in addition to a main motor which rotates the printing-form or plate cylinder and the distributor roller.
In the case of a printing machine wherein the rotation of the distributor roller and the rotation of the drive cam, and therefore the axial reciprocating or back-and-forth movement of the distributor roller, are driven by one and the same motor, for example, by the main motor which also drives the printing-form cylinder, the arrangement of a coupling device in a drive train which connects the drive cam to the motor can likewise permit the distributor roller to be stopped during the printing interruption. The coupling device, for example, in the form of an engageable clutch or a shift gear mechanism, can be linked with the printing unit via the control device. As a result, the control device can change over the coupling device based upon the switching of the printing unit, so that the drive cam can be uncoupled from the motor when printing is switched off, and coupled to the motor again when printing is switched on. During the printing interruption, the drive cam therefore does not rotate, and the distributor roller rotates without any axial distribution, so that, following the printing interruption, the inking profile needed to continue printing is established rapidly, and rejects are therefore avoided.
Another development which is advantageously made possible by the constructional conditions of the drive according to the invention includes the capability for the cycle rate of the axial oscillation of the distributor roller to be configured so that it can be set variably. By this cycle rate, there is meant the ratio between a number of revolutions of the printing-form cylinder and one complete axial oscillation of the distributor roller. If the motor rotating the drive cam is constructed as the separate motor mentioned hereinbefore, by the control device, the rotational speed thereof and, therefore, the rotational speed of the drive cam can be adjusted in various ratios with respect to the rotational speed of the main motor and, therefore, to the rotational speed of the printing-form cylinder, for example, so that, at one set rotational-speed ratio, the printing-form cylinder rotates once for each complete oscillation of the distributor roller (single-cycle distribution) and, at a different set rotational-speed ratio, rotates twice (half-cycle distribution).
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a drive for a distributor roller in a printing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.